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In order to ascertain the resistance mechanism of soil water stress on the growth of rice,explore the potential of rice production fully and improve the water productivity,it is quite necessary to carry out the research about the effects of different soil water treatments on photosynthetic characteristics and grain yield in rice.Thus a series of water gradient experiments were carried out on the basis of two different rice cultivars,involving Wuxiangjing14(Japonica Rice) and Liangyoupeijiu(Hybrid Rice).Four particular configured water supply levels,including continuous flooding irrigation(CK),20% soil water content(W1),30% soil water content(W2) and 40% soil water content(W3),were designed to analysis and investigate the photosynthetic characteristics,grain yield and its components,water productivity in rice.The research results showed that the two experimental cultivars had similar distributions of leaf stomatic conductance in the flag leavesunder the four soil water treatments during the different ricecritical growth stages,which were W3CKW2W1.In addition,the photosynthetic rates in the upper four leaves were the highest under low-grade soil dry stress treatment for it delayed aging of leaf,the distributions of photosynthetic rate under the four treatments were all represented as W3CK/W2W1,but the variations of transpiration rate were not significant.Besides,at the early filling stage,the distributions of leaf stomatic conductance,transpiration rate and photosynthetic rate at different leaf positions under four treatments were all represented as flag leaf upper second leaf upper third leaf upper fourth leaf.Moreover,the observations found that the transpiration rates of flag leaf were significantly higher than the others.Furthermore,the difference values between upper leaf and lower leaf in the cultivar of Liangyoupeijiu were greater than the difference values of Wuxiangjing14.Further comparing with the continuous flooding irrigation(CK),the grain yields of Wuxiangjing14 under the treatments of W1,W2 and W3 were decreased by 61.14%,29.13%,and increased by 0.96%,while for the experimental cultivar of Liangyoupeijiu,the grain yields were decreased by 64.11%,28.76%,and increased by 2.08%,respectively.Continuous flooding irrigation increased the dry matter,spike number and spikelet number per panicle,but low-grade soil dry stress treatment increased the seed setting rate and 1000-grain weight.In the other hand,the water productivities of Wuxiangjing14 and Liangyoupeijiu were also observed and measured under the different soil water treatments.The experimental results indicated that the water productivities of both two cultivars had overall trends of W3 CK/ W2 W1,where the highest values were appeared in the treatment of W3 with the values were 1.58 kg/m3 and 1.49 kg/m3,respectively.Further comparing with the continuous flooding irrigation(CK),the water productivities of Wuxiangjing14 under the treatments of W1,W2 and W3 were decreased by 10.69%,and increased by 1.53%,20.61%,respectively;while the water productivities of Liangyoupeijiu under the treatments of W1,W2 and W3 were decreased by 16.39%,and increased by 2.46%,22.13%,respectively.This research work would provide a technical support for precise irrigation management and water-saving production in rice.